1. Field of the Invention
This invention relates to handling of materials, and more particularly to a transfer system. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for removing static electricity generated by a frictional force in the course of transferring a substrate while fabricating a liquid crystal display device.
2. Description of the Related Art
In general, display devices are very important in conveying visual information in the information society. In the past, a cathode ray tube (CRT) was typically used as the display device. However, the cathode ray tube has the problems of heavy weight and bulky volume. To alleviate these problems of the CRT, flat panel display devices, including liquid crystal display device (LCD), a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence (EL), are introduced into the market.
An LCD device has thin profile and light-weight. Thus, the LCD device has been rapidly replacing the cathode ray tube in many applications. An active matrix type LCD device has a thin film transistor (hereinafter, TFT) for each cell area in a matrix of cell areas. The active matrix type LCD has the advantages of high picture quality and small power consumption.
FIG. 1 is a perspective view showing a liquid crystal display device of an active matrix type according to the related art. Referring to FIG. 1, the liquid crystal display device of the active matrix type includes a color filter array substrate 22 and a TFT array substrate 23, which are affixed to each other with a liquid crystal layer 15 therebetween. The liquid crystal display device shown in FIG. 1 is a portion of the whole display screen.
A black matrix (not shown), a color filter 13 and a common electrode 14 are on a rear side of an upper glass substrate 12 to form a color filter substrate 22. A polarizer 11 is attached on a front side of the upper glass substrate 12. The color filters 13 include red R, green G and blue B color filters to implement a color display.
In the TFT array substrate 23, data lines 19 and gate lines 18 cross each other on a front side of the lower glass substrate 16, and TFTs 20 are formed at the crossings. A pixel electrode 21 is formed at a cell area between the data line 19 and the gate line 18. The TFT 20 switches a data transmitting path between the data line 19 and the pixel electrode 21 in response to a scanning signal from the gate line 18 to drive the pixel electrode 21. A polarizer 17 is attached at the rear side of the TFT array substrate 23.
A liquid crystal layer 15 controls light transmitted through the TFT array substrate 23 by an electric field applied to the liquid crystal layer 15. An alignment film (not shown) is formed on the opposing surfaces of the color filter substrate 22 and the TFT substrate 23 adjacent to the liquid crystal layer 15. The polarizers 11 and 17 attached on the color filter substrate 22 and the TFT substrate 23 allow light polarized in only direction to be transmitted, and the polarizing directions of each of the polarizers 11 and 17 cross each other when the liquid crystal layer 15 is a 90° TN mode.
A method of fabricating a liquid crystal display device of the active matrix type includes substrate cleaning, substrate patterning, alignment forming/rubbing, substrate joining, liquid crystal injecting, packing, inspecting and repairing processes. The substrate cleaning process removes impurities contaminating the substrate surface using a cleaning solution. The substrate patterning process includes a patterning of the color filter array substrate and a patterning of the TFT-array substrate. In the alignment forming/rubbing process, alignment films are respectively coated on the color filter array substrate and the TFT array substrate, and then the alignment films are rubbed by a rubbing cloth. In the substrate joining/a liquid crystal injecting process, the color filter substrate and the TFT array substrate are joined each other by a sealant, and then liquid crystal molecules and spacers are injected through a liquid crystal injection port, which is later sealed. In the packing process of a liquid crystal display panel, a tape carrier package (hereinafter, TCP) is packed with a gate drive integrated circuit and a data drive integrated circuit, and then connected to a pad portion of the substrate. The drive integrated circuit can be directly packed onto the substrate by a Tape Automated Bonding using the above-mentioned TCP or a Chip On Glass (hereinafter, COG) type structure. The inspecting process includes an electrical inspection after a signal wiring, such as a data line and a gate line, and a pixel electrode are formed on the TFT array substrate, followed by another electrical inspection and a naked eye inspection after the substrate joining/the liquid crystal injecting process. The repairing process restores operation of a component on the substrates that the inspecting process indicates to be repairable. On the other hand, a substrate is discarded that the inspecting process indicates as be unrepairable.
In fabrication of most flat panel display device, including the liquid crystal display device, a thin film material disposed on the substrate is patterned by a photolithography process, and the photolithography process consists of a series of photo process, such as coating photo-resist, mask alignment, exposure, development and cleaning. When the photolithography process is completed, the substrate is transferred into another chamber for an etching and stripping process. The transfer system for transferring the substrate from one chamber to another chamber during fabricating of the flat panel display device can include a series of shafts having rollers thereon.
FIG. 2 is a perspective view showing a transfer system using a method of fabricating a related art liquid crystal display device. FIG. 3 is a perspective view showing rollers on a shaft in the transfer system of FIG. 2. As shown in FIG. 2, a transfer system 50 includes a plurality of shafts 51 arranged in such a manner as to have a constant spacing on the same plane and a plurality of rollers 52 on each of the shafts 51 with a constant spacing. The plurality of shafts 51 are supplied with a rotational force so as to rotate the shafts 51 with a constant velocity.
Referring to FIG. 3, a plurality of rollers 52 having a disk shape are affixed to the shaft 51, which passes through a middle portion of the disk shape. The plurality of rollers 52 are fixed on the shaft 51, so that the glass substrate 53 loaded on the transfer system 50 contacts the shaft 51 but directly contacts the rollers 52. Accordingly, if the shaft rotates with a constant velocity, the rollers 52 rotate along with the shaft 51 such that a frictional force between the rollers 52 and the glass substrate 53 is generated to move the glass substrate 130.
Recently, flat panel display devices are becoming very large. Thus, the size of the glass substrate is becoming very large. Accordingly, the shaft 51 length of the transfer system 50 for loading and transferring the large glass substrate is lengthened and more rollers are added to accommodate larger substrates. The frictional force generated between the rollers 52 and the glass substrate 53 can cause a static electricity charged on the glass substrate 53. More rollers generates more of a static electricity charge. Components on the glass substrate 53 can be damaged by such a static electricity charge. Thus, there is need to prevent static electricity so as to protect the components on the glass substrate 53 from damage.